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A case of acetohexamide-induced hypoglycemia: the influence of hypothyroidism on the metabolism of acetohexamide.

Prolonged hypoglycemia induced by acetohexamide (AH) in a patient with noninsulin dependent diabetes mellitus accompanied by primary hypothyroidism was presented. A 74-year-old man who had been treated with AH (500mg, daily) for diabetes mellitus since 1973 was admitted to our hospital in Oct. 1988 because of hypoglycemic coma. On admission, the level of blood glucose was 20mg/dl. Continuous intravenous administration of 10 per cent glucose solution led to improvement in the mental state on the second day. However, the level of blood glucose remained between 30 to 45mg/dl for four days after admission. On the fifth day, a fasting blood glucose level finally reached 75mg/dl. In a thyroid function test, the serum levels of thyroid hormone showed the following decreases: T3 68ng/dl, T4 2.8 micrograms/dl, free T4 0.3ng/dl, while basal TSH levels increased to 50.3 microU/ml. Since anti-thyroid microsomal antibody was positive and thyroid 99mTc-pertechnetate uptake was slightly elevated, the hypothyroidism in this patient was considered to be caused by chronic thyroiditis. Urinalysis was positive for protein. In a renal function test, the blood urea nitrogen was 26.7mg/dl and creatinine 1.7mg/dl, and creatinine clearance decreased to 22ml/min. After thyroid function returned to euthyroid, creatinine clearance improved (41 ml/min). To clarify the relationship between hypothyroidism and the metabolism of AH, the serum levels of AH and its metabolite hydroxyhexamide (HH) following oral administration of AH (500mg) were evaluated before and after thyroxine replacement therapy. The blood glucose level before therapy was lower than that after therapy, and hypoglycemic symptoms were observed early in the second and third morning after AH administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetohexamide↗

Sex-dependent pharmacokinetics and in vitro reductive metabolism of acetohexamide in Wistar-Imamichi rats.

A significant sex-related difference was observed for the pharmacokinetics of acetohexamide in Wistar-Imamichi (Wistar-IM) rats. However, there was no sex difference of the in vitro reductive metabolism of acetohexamide in the liver or kidney of these rats. Testectomy was found to decrease the plasma clearance (CLp) of acetohexamide in male rats, whereas ovariectomy had no effect on the CLp of acetohexamide in female animals, suggesting that androgens regulate the pharmacokinetics of acetohexamide. The co-administration of sulfamethazine, which is known to be metabolized by a male-specific cytochrome P450 (CYP) isoform (CYP2C11), significantly decreased the CLp of acetohexamide in male Wistar-IM rats. Based on these results, it is reasonable to assume that the sex-dependent pharmacokinetics of acetohexamide observed in Wistar-IM rats is associated with the male-specific hydroxylation catalyzed by CYP2C11.

Acetohexamide↗

Metabolic reduction of acetohexamide in rat kidney: sex difference and effect of streptozotocin-induced diabetes.

The acetohexamide reductase activity in 10000 x g supernatant fluids of kidney homogenates was significantly higher in male than in female rats. Although difference in activity of acetohexamide reductase in the cytosol between the sexes was not observed, the activity in the microsomes was considerably higher in male than in female rats. These findings indicate that the microsomal enzyme plays an important role in the sex difference of acetohexamide reduction by 10000 x g supernatant fluids of kidney homogenates. The sensitivities to inhibitors of microsomal acetohexamide reductase were different from those of cytosolic acetohexamide reductase. Furthermore, streptozotocin-induced diabetes significantly decreased acetohexamide reductase activity only in the kidney microsomes of male rats, resulting in the abolishment of the sex difference of acetohexamide reduction by 10000 x g supernatant fluids of kidney homogenates.

Acetohexamide↗

Carbonyl reductase activity for acetohexamide in human erythrocytes.

Acetohexamide is an oral antidiabetic agent and is metabolized by the reductive conversion of the acetoxy group to a secondary alcohol metabolite. In vivo, many drugs are metabolized by reductase enzymes; however, the characteristics of the enzymes that reduce carbonyl compounds need to be clarified. We tested whether reductase activity for acetohexamide can be found in human erythrocytes. Enzyme activity was monitored by formation of hydroxyhexamide using HPLC methods. In human erythrocytes, reductase activity (6.10 +/- 1.20 nmol/min/g hemoglobin) (mean +/- SD) was indeed observed, when 0.5 mM acetohexamide was used as a substrate. KM values and Vmax at the physiologically important pH 7.4 were 0.70 +/- 0.13 mM and 9.19 +/- 0.88 nmol/min/g hemoglobin, respectively. Separation of protein by gel filtration gave one major peak fraction with reductase activity whose molecular weight was estimated to be 31,000. Known substrates of carbonyl reductase such as menadione, daunorubicin, and ethacrynic acid inhibited the acetohexamide reduction. The acetohexamide reductase in erythrocyte showed characteristics of carbonyl reductase. Furthermore, acetohexamide reductase activity in erythrocyte was approximately 30% activity of that of human liver (0.17 +/- 0.05 nmol/min/mg cytosolic protein). The pattern of inhibitors in human liver was essentially the same as that in erythrocytes. It is plausible that the activity in erythrocytes may predict the activity in the liver. It was concluded that carbonyl reductase in human erythrocyte plays an important role in acetohexamide metabolism.

Acetohexamide↗

20beta-hydroxysteroid dehydrogenase catalyzes ketone-reduction of acetohexamide, an oral antidiabetic drug, in liver microsomes of adult male rats.

We examined the catalytic properties and physiological function of an enzyme responsible for the ketone-reduction of acetohexamide, an oral antidiabetic drug, in liver microsomes of adult male rats. Progesterone, 17alpha-hydroxyprogesterone, cortisone and cortisol, which have a ketone group at 20-position of C21-steroids, were potent inhibitors for ketone-reduction of acetohexamide in liver microsomes of adult male rats. Progesterone was also found to inhibit competitively the ketone-reduction of acetohexamide, suggesting that the ketone-reduction of acetohexamide and progesterone is catalyzed by the same enzyme. When progesterone was used as a substrate, 20beta-hydroxysteroid dehydrogenase present in liver microsomes of adult rats, such as acetohexamide reductase, exhibited a male-specific and androgen-dependent activity. Furthermore, a significant correlation was observed between the activities of 20beta-hydroxysteroid dehydrogenase and acetohexamide reductase in liver microsomes of individual male rats at various ages. Based on all results, we conclude that 20beta-hydroxysteroid dehydrogenase catalyzes the ketone-reduction of acetohexamide in liver microsomes of adult male rats.

Acetohexamide↗

Purification and catalytic properties of a novel acetohexamide-reducing enzyme from rabbit heart.

An enzyme catalyzing the metabolic reduction of acetohexamide [4-acetyl-N-(cyclohexyl-carbamoyl)benzenesulfonamide], an oral antidiabetic drug, was purified to homogeneity from the cytosolic fraction of rabbit heart. The molecular mass of the purified enzyme was estimated to be 110 kDa by gel filtration and nondenaturing PAGE and 28 kDa by SDS-PAGE, suggesting that the enzyme is composed of four identical-size subunits. 4-Benzoyl-pyridine and p-nitroacetophenone, typical substrates of carbonyl reductase [EC 1.1.1.184], were not reduced by the enzyme. Of drugs with a ketone group tested, only acetohexamide was a good substrate of the enzyme. the enzyme effectively reduced analogs substituted with various alkyl groups instead of the cyclohexyl group in acetohexamide, although it had little or no ability to reduce analogs substituted with various alkyl groups instead of the methyl group in acetohexamide. The enzyme was inhibited not only by quercetin, a well-known inhibitor of carbonyl reductase, but also by phenobarbital, a potent inhibitor of aldehyde reductase [EC 1.1.1.2]. These results indicate that the enzyme purified from rabbit heart is a novel enzyme responsible for the reduction of acetohexamide and its analogs.

Acetohexamide↗

In vivo and in vitro binding of (-)-hydroxyhexamide, a major metabolite of acetohexamide, to rabbit serum.

The in vivo and in vitro bindings of (-)-hydroxyhexamide, a major metabolite of acetohexamide, to rabbit serum were examined by using an ultrafiltration method. The in vivo serum protein binding of (-)-hydroxyhexamide was much lower than the in vitro serum protein binding. The in vitro serum protein binding of (-)-hydroxyhexamide was strongly displaced by the addition of acetohexamide. Furthermore, the in vitro serum protein binding of (-)-hydroxyhexamide in the presence of acetohexamide and (-)-hydroxyhexamide at the same concentrations as those found 1.0 h after acetohexamide administration was approximately similar to the in vivo serum protein binding of (-)-hydroxyhexamide. These results lead us to conclude that acetohexamide, the parent drug of (-)-hydroxyhexamide, plays an important role in the in vivo serum protein binding of (-)-hydroxyhexamide.

Acetohexamide↗

Combined testosterone treatment in pubertal and adult periods induces male-specific acetohexamide reductase activity in liver microsomes of female rats.

The influence of testosterone treatment on acetohexamide reductase activities in liver microsomes and cytosol of female rats was examined. Acetohexamide reductase activity in liver microsomes was much lower in female rats than in male rats. Combined testosterone treatment in pubertal and adult periods induced male-specific acetohexamide reductase activity in liver microsomes of female rats. However, testosterone treatment only during puberty or during adulthood was without effect. Testosterone secreted from the testes during puberty appeared to have a significant effect similar to neonatal imprinting in the induction of acetohexamide reductase activity in liver microsomes of female rats. The combined testosterone treatment, or testosterone treatment only during puberty or during adulthood had no effect on acetohexamide reductase activity in liver cytosol of female rats.

Aging↗

Cadmium exposure decreases androgen-dependent metabolism of acetohexamide in liver microsomes of male rats through its testicular toxicity.

Administration of cadmium (Cd) at a dose of 1.23 mg/kg (2.0 mg/kg as CdCl(2)) markedly decreased the activity of an enzyme (acetohexamide reductase) catalysing the ketone-reduction of acetohexamide, an oral antidiabetic drug, in liver microsomes of male rats. However, the decreased enzyme activity was increased by repeated treatment with testosterone propionate (TP). When male rats were castrated and TP was given to the castrated ones, a similar decrease and increase, as described above, were observed in the microsomal enzyme activity. Cd exposure to male rats induced haemorrhage and atrophy of the testes and significantly diminished serum testosterone levels. There was no possibility that Cd accumulated in liver microsomes of male rats causing direct inhibition of the microsomal enzyme activity. We conclude that Cd exposure decreases androgen-dependent metabolism of acetohexamide in liver microsomes of male rats through its testicular toxicity. Cd exposure had no effect on acetohexamide reductase activity in liver cytosol of male rats.

Acetohexamide↗

Hypoglycemic effect of S(-)-hydroxyhexamide, a major metabolite of acetohexamide, and its enantiomer R(+)-hydroxyhexamide.

A short-lasting hypoglycemic effect was observed when S(-)-hydroxyhexamide (S-HH), a major metabolite of acetohexamide, and its enantiomer R(+)-hydroxyhexamide (R-HH), were administered orally to rats. Since the reductive metabolism of acetohexamide is known to be reversible in rats, oral administration of R-HH may exhibit the hypoglycemic effect through the generation of acetohexamide. However, oral administration of R-HH to rabbits, in spite of their inability to oxidize R-HH to acetohexamide, caused a significant decrease and increase, respectively, of plasma glucose and insulin levels. Furthermore, both S-HH and R-HH were found to stimulate the secretion of insulin from hamster HIT T15 cells (pancreatic beta-cells). These results provide further evidence that both R-HH and S-HH exhibit a significant hypoglycemic effect.

Acetohexamide↗

Characterization of acetohexamide reductases purified from rabbit liver, kidney, and heart: structural requirements for substrates and inhibitors.

The structural requirements of acetohexamide reductases purified from rabbit liver, kidney, and heart for substrates and inhibitors were examined. Acetohexamide, an oral antidiabetic drug with a ketone group, and analogs of it with various alkyl groups instead of the cyclohexyl group were used as substrates for these three enzymes. The results obtained as to substrate specificity suggested that the nature of the substrate-binding region of the heart enzyme is markedly different from those of the substrate-binding regions of the liver and kidney enzymes. Tolbutamide, which has no ketone group within its chemical structure, strongly inhibited the heart enzyme, whereas it had little ability to inhibit the liver or kidney enzyme. The inhibition of the heart enzyme by tolbutamide was competitive with respect to acetohexamide and uncompetitive with respect to NADPH. Furthermore, tolbutamide analogs with n-pentyl and n-hexyl groups instead of the n-butyl group exhibited very pronounced inhibition of only the heart enzyme. Therefore, it is reasonable to postulate that the heart enzyme, unlike the liver and kidney ones, has a cleft of a strongly hydrophobic nature near its substrate-binding region, and that this hydrophobic cleft plays a critical role in the interaction of the heart enzyme with the cyclohexyl group of acetohexamide.

Acetohexamide↗

Acetohexamide hypoglycemia: treatment by peritoneal dialysis.

Acetohexamide hypoglycemia in a patient with renal failure has been successfully treated by peritoneal dialysis. Peritoneal dialysis was done in such a patient, and specimens of serum were collected to measure levels of acetohexamide and its main active metabolite, hydroxyhexamide. During dialysis, hypoglycemia was corrected. After 17 1/2 hours of dialysis, serum acetohexamide level was essentially unchanged. Serum hydroxyhexamide level had decreased at a slower rate than the rate of decrease previously measured in a uremic patient not on dialysis. Although peritoneal dialysis may correct the hypoglycemia, the data suggest that acetohexamide and hydroxyhexamide are not dialyzable. Due to these problems this drug should not be used in patients with chronic renal failure. The drug of choice to control hyperglycemia in patients with renal insufficiency is insulin. If for any reason insulin cannot be used, tolbutamide is the oral hypoglycemic agent of choice.

Acetohexamide↗

Alteration of acetohexamide reductase activities in kidney microsomes and cytosol of cadmium-treated rats.

We examined the alteration of acetohexamide reductase activities in kidney microsomes and cytosol of cadmium (Cd)-treated rats. Acetohexamide reductase activity in kidney microsomes of male rats was markedly decreased by treatment with Cd at a dose of 1.23 mg/kg body weight. However, the decreased enzyme activity was completely restored by repeated treatment with testosterone propionate. Therefore, it is reasonable to assume that the treatment with Cd indirectly affect the androgen-dependent acetohexamide reductase activity in kidney microsomes of male rats, possibly by depressing androgen production. In the case of female rats, unlike male rats, the microsomal enzyme activity was little detectable, and was unaffected by the treatment with Cd. Furthermore, Cd treatment had no significant effect on acetohexamide reductase activity in kidney cytosol of male or female rats.

Alcohol Oxidoreductases↗

Influence of aging on acetohexamide reductase activities in liver microsomes and cytosol of male rats.

The influence of aging on the reductase activity of acetohexamide, an oral antidiabetic drug with a ketone group, was examined in liver microsomes and cytosol of male rats. Acetohexamide reductase activities in liver microsomes of male rats at 26 and 31 months of age were much lower than that in liver microsomes of male rats at 9 weeks of age. Testectomy markedly decreased acetohexamide reductase activity in liver microsomes of the 9-week old rats and the decreased enzyme activity was significantly increased by testosterone administration. These results indicate, at least in part, that aging decreases the enzyme activity by decreasing the secretion of testosterone from the testes. On the other hand, aging (26 months of age) did not affect acetohexamide reductase activity in liver cytosol of male rats, although the enzyme activity at 31 months of age was slightly but significantly lower than that in liver cytosol of male rats at 9 weeks of age. Testectomy or testosterone administration had no effect on the enzyme activity in liver cytosol of 9-week old male rats.

Aging↗

Individual variation of acetohexamide reductase activities in liver microsomes and cytosol of rats.

We examined individual variations in acetohexamide reductase activities in liver microsomes and cytosol of rats. Large differences among individuals were observed for acetohexamide reductase activity in liver microsomes of male Fischer-344 (Fischer), Sprague-Dawley (SD) and Wistar rats at 9 weeks of age, except in the Wistar-Imamichi (Wistar-IM) strain. These four strains of female rats did not exhibit any microsomal enzyme activity. Although acetohexamide reductase activities were fully detectable in liver cytosols from all the strains of male and female rats, there was neither strain-related difference nor considerable individual variation in the cytosolic enzyme activity. In liver microsomes of male Fischer rats at 4 weeks of age, acetohexamide reductase activity was not detectable. The microsomal enzyme activity in male Fischer rats markedly increased at 6 weeks of age to approach the levels at 9 and 12 weeks of age, with large individual variations.

Aging↗

Bioassay of acetohexamide for possible carcinogenicity.

A bioassay of acetohexamide for possible carcinogenicity was conducted by administering the test chemical in feed to Fischer 344 rats and B6C3F1 mice. Groups of 35 rats of each sex were administered acetohexamide in the diet at one of two doses, either 10,000 or 20,000 ppm, for 103 weeks and then observed for 2 to 4 additional weeks. Matched controls consisted of 15 untreated rats of each sex. All surviving rats were killed at 105 to 107 weeks. Groups of 35 mice of each sex were administered acetohexamide at one of two doses for 103 weeks and then observed for 4 or 5 additional weeks. Time-weighted average doses were 6,359 or 12,718 ppm. Matched controls consisted of 15 untreated mice of each sex. All surviving mice were killed at 107 or 108 weeks. Mean body weights of the dosed rats and mice of both sexes were lower than those of the corresponding matched controls throughout the study, and the depressions in weight were dose related. Except for the female mice, sufficient numbers of animals survived long enough to be at risk for development of late-appearing tumors. In the rats, the only tumor occurring with greater incidence in dosed than in matched-control animals was leukemia (males: matched controls 0/15, low-dose 10/35, high-dose 4/35; females: matched controls 0/14, low-dose 7/35, high-dose 4/34). Only the incidence in the low-dose males was statistically significant (P=0.018). All of these animals had undifferentiated (mononuclear cell) leukemia, which commonly occurs spontaneously in Fischer 344 rats, except for two with lymphocytic leukemia. The incidence of combined leukemia and lymphoma in historical-control male rats at this laboratory in the bioassay program to date is 24/235 (10.2%), which is higher than that in the matched controls. Thus, the incidence in the low-dose males cannot be clearly associated with administration of the test chemical. In the mice, the only neoplasms that occurred at a higher incidence in dosed groups than in matched controls were lymphomas in the males, but the incidences were not statistically significant (matched controls 1/15, low-dose 9/35, high-dose 3/34). These types of lesions are found commonly in untreated B6C3F1 mice. The incidence of lymphomas in the historical-control male mice is 28/536 (5.2%). It is concluded that under the conditions of this bioassay, acetohexamide was not carcinogenic for either Fischer 344 rats or B6C3F1 mice.

Journal Article↗

Postnatal development of acetohexamide reductase activities in microsomes and cytosol of rat liver.

The postnatal development of acetohexamide reductase activities in liver microsomes and cytosol were examined in male rats. The developmental pattern of acetohexamide reductase activity in liver microsomes was distinguished from that in liver cytosol. Furthermore, acetohexamide reductase activity in liver microsomes was effectively suppressed by castration, but the activity in liver cytosol was not affected by castration. These results clearly indicate that enzymes with physiologically different roles can catalyze the metabolic reduction of acetohexamide in rat liver.

Age Factors↗

Drug-metal interactions: copper(II) complex of the antidiabetic drug acetohexamide and pyridine.

The preparation, spectral properties, and crystal structure of a copper(II) complex of 4-acetyl-N-[(cyclohexylamino)carbonyl]benzenesulfonamide, which is known as acetohexamide, and pyridine are reported. The complex Cu(AH)2(py)2, where AH = acetohexamide and py = pyridine, was prepared and characterized by X-ray and ESR. The complex is monoclinic, space group P2(1)/a, with a = 17.412(6), b = 9.039(2), c = 26.531(10) A, beta = 102.24(2) degrees, and Z = 4. The final refinement used 3892 unique reflections and gave an R value of 0.0646. The copper atom is surrounded by four nitrogen atoms in a square-planar arrangement, two from the acetohexamide ligands (Cu-N = 2.009 A) and two from the pyridine molecules (Cu-N = 2.016 A) in a trans geometry. The ESR data support a similar coordination behavior of the copper (g parallel greater than g perpendicular greater than ge) with the unpaired electron in the dx2-y2 orbital.

Acetohexamide↗